Toward the end of filmmaker Joe Berlinger’s documentary “Whitey: United States of America v. James J. Bulger,” US Attorney Carmen Ortiz stands outside US District Court in South Boston and proudly announces that the mob boss’s conviction marks “the end of an era that was very ugly in Boston’s history.” Berlinger doesn’t buy it. In his film, which screens Thursday at the Coolidge Corner Theatre, the director asserts that the Bulger saga cannot be fully understood until the FBI’s complicity in Whitey’s reign is investigated. “The thing the film does most strongly,” the director told us Tuesday, “is raise the visibility of certain questions: Was he an informant or wasn’t he? And did he have immunity or didn’t he?” But unless you have a ticket, don’t bother showing up in Brookline. The screening sold out so quickly that some relatives of Bulger’s victims couldn’t get in. (For that reason, Berlinger is giving his own two tickets to the families of Edward Connors and William O’Brien, two of Whitey’s victims.) Berlinger says he was initially reluctant to make a movie about Bulger, feeling he had little to add to the avalanche of media and books on the topic. “But at the end of 2012, when a trial date was actually set — the biggest trial in Massachusetts since Sacco and Vanzetti — I thought I could add to the canon and separate the man from the myth.” And a courthouse is clearly where Berlinger is comfortable, as demonstrated in his earlier docs “Brother’s Keeper” and the “Paradise Lost” trilogy. “Whitey” will eventually get a limited theatrical run — “it ain’t a blockbuster,” says Berlinger — and will air later this year on CNN, which financed the film. “I have to say, this is a very intense, sad, complicated story,” said the director. “But I really enjoyed working in Boston and getting to know the city. . . . I also happen to love ‘The Departed’ as a movie and I love [Martin] Scorsese, but that’s got about as much to do with Bulger as . . . well, it has very little to do with Bulger.” Asked about the two Bulger biopics currently in the works, Berlinger said the one starring Johnny Depp as Whitey is getting a lot of buzz, but the movie Ben Affleck and Matt Damon are working on is also progressing. “[Warner Bros. executive] Sarah Schechter went to our screening at Sundance and was very enthused,” said Berlinger. “It seems like their project is very real.”